The multi-billion-dollar program intended to revolutionize air travel in the United States is “stalled,” “broken” and not going to materialize “any time soon,” three frustrated members of Congress said at a hearing Tuesday.

At a cost of an estimated $40 billion to be shared by the government and the airline industry, the creation of a system known as NextGen has been entrusted to the Federal Aviation Administration, an agency renowned for its cautious and methodical implementation of change.

“It’s just apparent that the process is broken,” said Bill Shuster (R-Pa.), House Transportation Committee chairman. The FAA is “moving at a snail’s pace. We’ve got to get these things up and running.”

NextGen, or Next Generation Air Transportation System, is a vast interlocking array of technology that promises to reduce delays, fuel use and carbon footprints, while allowing for projected growth in the airline industry.

The FAA, which said it would launch NextGen a decade ago, was not invited to testify before the committee Tuesday.

A committee spokesman said FAA Administrator Michael Huerta would be asked to appear before the panel as it continues to explore a new funding authorization for the agency.

Judging from the frustration expressed by committee members Tuesday, Huerta can expect what will be a rocky day. Rep. Mark Meadows (R.-N.C.) recalled an earlier visit by Huerta and his deputies. “When we ask for deadlines, when we ask for time frames, I see sweat pop out on their foreheads. There’s not an answer,” Meadows said.

Setting deadlines, meeting goals and persuading the airlines that both will be achieved is critical to the success of NextGen. While airlines began to invest in some of the equipment the system requires, fear that the FAA will falter has made them cautious of heavy spending.

“Business leaders are concerned about the slow and uncertain pace of FAA efforts,” said John Engler, the former Michigan governor who now heads the Business Roundtable, an association of chief executive officers of leading U.S. companies.

While Lee Moak, president of the Air Line Pilots Association, said that NextGen was “on the verge of becoming a success story,” few members of the committee were prepared to embrace that belief.

“I think NextGen is either in a stall or a reverse. That’s not acceptable,” said Rep. John L. Mica (R.-Fla.), the former chairman of the House Transportation Committee.

Mica said he stepped down with “a sigh of relief” that no major domestic airline accident had occurred during his tenure as chairman. Alluding to the safety enhancements promised by NextGen, he said, “The clock is ticking. It can be an air traffic controller, it can be a pilot error.”

The challenge of replacing a 20th-century radar-based system with a technologically efficient GPS-based system was described as out of reach by Del. Eleanor Holmes Norton (D-D.C.), a non-voting member of Congress.

“We’re not going to do that anytime soon,” said Norton, who reacted to repeated reminders from those testifying that the United States has the safest aviation system in the world.

“I believe we have a safe system because you slow things down to make it safe,” she said. “That 2020 date [for partial implementation of NextGen] that was set some time ago is a fiction. It’s better to have that sort of candor than to have people being angry at the airport. Be candid so that the public does not expect anything but slow-downs for the foreseeable future.”

NextGen has been described as the antidote to gridlock in the air travel system, which is projected to be serving 1 billion passengers a year by 2021.

With the help of GPS, planes would be able to safely travel packed skies closer to other planes. They would be able to fly direct routes, unlike in the current system, which relies heavily on flying to waypoints before turning to a final destination.

Direct routing would allow airlines to save billions in fuel costs and minimize pollution. It also would permit far more precise choreography of planes at airports, reducing the amount of fuel wasted waiting for takeoff or burned because planes ready to land are diverted into holding patterns.

For passengers, NextGen would cut flight delays, eliminate time spent on the runway waiting to take off and shorten the flight time once airborne. In addition, fuel savings might result in lower ticket prices.